High Capacity Capacitors have been used in the semiconductor industry for years, in applications such as DRAM storage, protection from high energy environments, decoupling capacitors and many more. As integrated circuits continue to become more densely built, small and powerful decoupling capacitors are needed for optimal system performance.
A promising high-density capacitor for radio-frequency decoupling applications is reported by Klootwijt, et al., Ultrahigh Capacitance Density for Multiple ALD-Grown MIM Capacitor Stacks in 3-D Silicon”, IEEE Electron Device Letters, 29:7, July 2008 (hereafter the “Philips MIM capacitor”). Klootwijt et al discloses a method to form the 3-D capacitor 100 illustrated in FIG. 1. According to Klootwijt et al, a macropore 110 of about 1.5 micron diameter and 30 micron depth is formed in a substrate 101 that is “(arsenic) n++-doped silicon.” A 5-nm thermally grown SiO2 layer 121 coats the walls of the pore, then a “stack [125] of TiN/Al2O3/TiN/Al2O3/TiN is deposited by ALD” to complete the triple MIM capacitor stack. Conditions are controlled to avoid oxidation of the TiN electrode layers. “On completion, the layers are patterned for contacting the electrodes and covered with a low-temperature interlevel oxide layer. Finally, contact holes are opened, and bond pads 131 to 134 are formed.”
The process described by the above reference requires multiple lithography steps. What is needed is a simplified process to form an ultra-high density trench capacitor.